1. Field of the Invention
This invention relates to communication systems. More particularly, the invention relates to a server-workstation network with dynamic load balancing of messages in both the server inbound and outbound directions.
2. Related Patent Application
This patent application is related to copending U.S. patent application Ser. No. 08/297,469, filed Aug. 29, 1994, now abandoned which is a U.S. counterpart application of UK Patent Application GB 2281793, published Mar. 15, 1995 and filed Nov. 9, 1993 by G. D. Wallis et al and assigned to the same assignee as that of the present invention.
3. Description of the Prior Art
Routing, bridging and switching are existing techniques to optimize performance between workstations and servers. Recently, load balancing software has been introduced to further improve performance between work stations and servers. Load balancing software allows you to place multiple Network Interface Cards (NICs) into a server and attach the cards to one logical network. In addition, multiple balanced networks can be connected to one server. Normally, under load balancing software or other operating systems, a system administrator would assign a unique address to each NIC. With load balancing software, the NICs can be bound to one logical address, providing load sharing (balancing) across the server bus.
In operation, load balancing software uses dynamic balancing for outgoing traffic (data from the server to the workstation) and static balancing for incoming traffic (from the workstation to the server).
Dynamic balancing works by sending packets to each NIC in turn. For example, with four NICs in the server, the first packet is routed to NIC number 1; the second packet to NIC number 2; the third packet is routed to NIC number 3; the fourth packet to NIC number four; such that each NIC transmits every fourth packet.
Static balancing works differently. When a workstation wishes to connect to a server, it finds the Media Access Control (MAC) layer destination address of the server by sending a request, for example, an Address Resolution Protocol (ARP) on to the network. The address returned by the server in response to the ARP request is used by that workstation until further notice. The software assigns response addresses in round-robin fashion. NIC number 1 is assigned to workstations 1, 5, 9 and 13; NIC number 2 is assigned to workstations 2, 6, 10 and 14; NIC number 3 is assigned to workstations 3, 7, 11 and 15 and so forth. If, for example, workstations 1, 5 and 9 all transmit essentially simultaneously (with static balancing) the server NICs will become unbalanced. That is, NIC number 1 will be overloaded while NICs 2-4 will be idle. As a result, the latency for each workstation will increase and the throughput on the network will decrease by the unbalanced loading of the NICs.
The present invention is directed to improving both the latency and the throughput on a network having a plurality of workstations coupled through a network switch to a server having multiple entry ports.
The prior art addressing load balancing on related networks is as follows:
U.S. Pat. No. 5,031,089 issued Dec. 30, 1988, describes a dynamic resource allocation scheme for distributed heterogeneous computer systems. A decentralized resource sharing scheme is distributed over several compute engines in the network. The disclosure requires a computation of a "workload value" and the transmission thereof to all nodes on the network.
U.S. Pat. No. 5,025,491 issued Oct. 26, 1989, describes dynamic address binding in communication networks. '491 patent describes the relocation of servers, for example in the event of a "crash", and the rerouting of messages to a new server.
U.S. Pat. No. 5,271,003 issued Mar. 9, 1990, describes an internal routing method for load balancing. The '003 patent relates to rerouting messages in the event of a failed "message handling processor" in "circuit switched" networks.
U.S. Pat. No. 5,193,151 issued Aug. 30, 1989, describes a delay based congestion avoidance in computer networks. The '151 patent discloses a method to reduce traffic load based on a metric such as round-trip delay for a message and its associated acknowledgement.
U.S. Pat. No. 5,249,290 issued Feb. 22, 1991, describes a client/server computer network where the server uses a busy indicator to assign a new client service request to the least busy processor. The '290 patent uses a workload metric to assign "client" server requests to "servers".
U.S. Pat. No. 5,293,488 describes a message routing apparatus that uses a Network Interface Card for each network and a shared routing manager. The '488 patent relates to "filtering" messages or frames in a routing environment to decide whether or not to forward the message or frame to a particular network.
U.S. Pat. No. 5,241,677 describes a multi-processor system and a method of load balancing. The '677 patent balances the computational load on processors to maximize multi-processing efficiency.
IBM Technical Disclosure Bulletin, Volume 37, Number 07, published July 1994, describes a remote log-in program to balance processing load. The publication discloses assigning a "client" to the least loaded "server" as measured by a non-specific metric.
None of the prior art describe a communication network including a network server with multiple Network Interface Cards coupled to a plurality of workstations through a network switch, the in-bound and out-bound messages to/from the server being dynamically balanced to improve latency, throughput and recovery from fault conditions on the network.